CCIE ISP-Inter-AS MPLS solutions - Back-to-Back vrf’s

作者：佚名 2009-10-22 10:18:45

This post is about option A. I will show how to configure inter-as vpn’s using back-to-back vrf’s. Below you can see the diagram used for the purpose of this post.

When configuring inter-as mpls vpn’s you’ve got 3 options to choose from.

A - Back-to-Back VRF’s

B - MP-eBGP for VPNv4

C - Multi-hop EBGP VPNv4

This post is about option A. I will show how to configure inter-as vpn’s using back-to-back vrf’s. Below you can see the diagram used for the purpose of this post.

With back-to-back vrf’s what you’ll do is basically make the connected PE’s think of each other as CE’s. You can run any supported PE-CE routing protocol over the per VPN logical interface between the directly connected ASBR’s. This option is seen as the easiest one to configure, a drawback is that this option doesn’t scale very well as the numbers of VPN’s start to grow.

Below the working configurations for this inter-as solution, I left out the configurations for router R1, R5, R7 and R8 because there is nothing special configured on these routers (they’re just simple P-routers and CE routers running RIPv2).

R2 :

hostname R2
!
ip cef
!
ip vrf VPN_A
 rd 2.2.2.2:1
 route-target export 2.2.2.2:1
 route-target import 3.3.3.3:1
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface Loopback1
 ip vrf forwarding VPN_A
 ip address 22.22.22.22 255.255.255.255
!
interface FastEthernet0/0
 ip vrf forwarding VPN_A
 ip address 24.24.24.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/0
 ip address 12.12.12.2 255.255.255.0
 duplex auto
 speed auto
 tag-switching ip
!
router ospf 100 vrf VPN_A
 log-adjacency-changes
 redistribute bgp 123 subnets
 network 22.22.22.22 0.0.0.0 area 0
 network 24.24.24.2 0.0.0.0 area 0
!
router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 2.2.2.2 0.0.0.0 area 0
 network 12.12.12.2 0.0.0.0 area 0
!
router bgp 123
 bgp router-id 2.2.2.2
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 3.3.3.3 remote-as 123
 neighbor 3.3.3.3 update-source Loopback0
 !
 address-family vpnv4
 neighbor 3.3.3.3 activate
 neighbor 3.3.3.3 send-community both
 exit-address-family
 !
 address-family ipv4 vrf VPN_A
 redistribute ospf 100 vrf VPN_A match internal external 1 external 2
 no auto-summary
 no synchronization
 exit-address-family

R4 :

hostname R4
!
ip cef
!
ip vrf VPN_A
 rd 4.4.4.4:1
 route-target export 4.4.4.4:1
 route-target import 6.6.6.6:1
!
interface Loopback0
 ip address 4.4.4.4 255.255.255.255
!
interface Loopback1
 ip vrf forwarding VPN_A
 ip address 44.44.44.44 255.255.255.255
!
interface FastEthernet0/0
 ip vrf forwarding VPN_A
 ip address 24.24.24.4 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/0
 ip address 45.45.45.4 255.255.255.0
 duplex auto
 speed auto
 tag-switching ip
!
router ospf 100 vrf VPN_A
 log-adjacency-changes
 redistribute bgp 456 subnets
 network 24.24.24.4 0.0.0.0 area 0
 network 44.44.44.44 0.0.0.0 area 0
!
router ospf 1
 router-id 4.4.4.4
 log-adjacency-changes
 network 4.4.4.4 0.0.0.0 area 0
 network 45.45.45.4 0.0.0.0 area 0
!
router bgp 456
 bgp router-id 4.4.4.4
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 6.6.6.6 remote-as 456
 neighbor 6.6.6.6 update-source Loopback0
 !
 address-family vpnv4
 neighbor 6.6.6.6 activate
 neighbor 6.6.6.6 send-community both
 exit-address-family
 !
 address-family ipv4 vrf VPN_A
 redistribute ospf 100 vrf VPN_A match internal external 1 external 2
 no auto-summary
 no synchronization
 exit-address-family

#p3

R3 :

hostname R3
!
ip cef
!
ip vrf VPN_A
 rd 3.3.3.3:1
 route-target export 3.3.3.3:1
 route-target import 2.2.2.2:1
!
interface Loopback0
 ip address 3.3.3.3 255.255.255.255
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
!
interface FastEthernet1/0
 ip address 13.13.13.3 255.255.255.0
 duplex auto
 speed auto
 tag-switching ip
!
interface FastEthernet2/0
 ip vrf forwarding VPN_A
 ip address 37.37.37.3 255.255.255.0
 duplex auto
 speed auto
!
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 network 3.3.3.3 0.0.0.0 area 0
 network 13.13.13.3 0.0.0.0 area 0
!
router rip
 version 2
 no auto-summary
 !
 address-family ipv4 vrf VPN_A
 redistribute bgp 123 metric transparent
 network 37.0.0.0
 no auto-summary
 exit-address-family
!
router bgp 123
 bgp router-id 3.3.3.3
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 2.2.2.2 remote-as 123
 neighbor 2.2.2.2 update-source Loopback0
 !
 address-family vpnv4
 neighbor 2.2.2.2 activate
 neighbor 2.2.2.2 send-community both
 exit-address-family
 !
 address-family ipv4 vrf VPN_A
 redistribute rip
 no auto-summary
 no synchronization
 exit-address-family

R6 :

hostname R6
!
ip cef
!
ip vrf VPN_A
 rd 6.6.6.6:1
 route-target export 6.6.6.6:1
 route-target import 4.4.4.4:1
!
interface Loopback0
 ip address 6.6.6.6 255.255.255.255
!
interface FastEthernet0/0
 ip vrf forwarding VPN_A
 ip address 61.61.61.6 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/0
 ip address 56.56.56.6 255.255.255.0
 duplex auto
 speed auto
 tag-switching ip
!
interface FastEthernet2/0
 ip vrf forwarding VPN_A
 ip address 68.68.68.6 255.255.255.0
 duplex auto
 speed auto
!
router ospf 1
 router-id 6.6.6.6
 log-adjacency-changes
 network 6.6.6.6 0.0.0.0 area 0
 network 56.56.56.6 0.0.0.0 area 0
!
router rip
 version 2
 no auto-summary
 !
 address-family ipv4 vrf VPN_A
 redistribute bgp 456 metric transparent
 network 68.0.0.0
 no auto-summary
 exit-address-family
!
router bgp 456
 bgp router-id 6.6.6.6
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 4.4.4.4 remote-as 456
 neighbor 4.4.4.4 update-source Loopback0
 !
 address-family vpnv4
 neighbor 4.4.4.4 activate
 neighbor 4.4.4.4 send-community both
 exit-address-family
 !
 address-family ipv4 vrf VPN_A
 redistribute rip
 no auto-summary
 no synchronization
 exit-address-family

As you can see we run a separate instance of the OSPF process between router R2 and R4, under this process we redistribute BGP.

Now let’s do a “show ip route” on router R7 :

R7 :

R7#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     68.0.0.0/24 is subnetted, 1 subnets
R       68.68.68.0 [120/2] via 37.37.37.3, 00:00:07, FastEthernet1/3
     37.0.0.0/24 is subnetted, 1 subnets
C       37.37.37.0 is directly connected, FastEthernet1/3
     22.0.0.0/32 is subnetted, 1 subnets
R       22.22.22.22 [120/1] via 37.37.37.3, 00:00:07, FastEthernet1/3
     7.0.0.0/32 is subnetted, 1 subnets
C       7.7.7.7 is directly connected, Loopback0
     8.0.0.0/32 is subnetted, 1 subnets
R       8.8.8.8 [120/2] via 37.37.37.3, 00:00:07, FastEthernet1/3
     24.0.0.0/24 is subnetted, 1 subnets
R       24.24.24.0 [120/1] via 37.37.37.3, 00:00:07, FastEthernet1/3
     44.0.0.0/32 is subnetted, 1 subnets
R       44.44.44.44 [120/3] via 37.37.37.3, 00:00:09, FastEthernet1/3

As you can see router R7 can see router R8

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